MUST KNOW iii – x Chapter 1 Introduction to Chemistry 1 – 9 NOTES 1 Paper 1 3 Paper 2 6 Paper 3 9 Chapter 2 Matter and the Atomic Structure 10 – 25 NOTES 10 Paper 1 12 Paper 2 19 Paper 3 25 Chapter 3 The Mole Concept, Chemical Formula and Equation 26 – 39 NOTES 26 Paper 1 27 Paper 2 33 Paper 3 39 Chapter 4 The Periodic Table of Elements 40 – 53 NOTES 41 Paper 1 42 Paper 2 48 Paper 3 53 Chapter 5 Chemical Bond 54 – 68 NOTES 54 Paper 1 56 Paper 2 61 Paper 3 68 Chapter 6 Acid, Base and Salt 69 – 88 NOTES 69 Paper 1 75 Paper 2 81 Paper 3 87 Chapter 7 Rate of Reaction 89 – 107 NOTES 89 Paper 1 91 Paper 2 100 Paper 3 107 Chapter 8 Manufactured Substances in Industry 108 – 125 NOTES 108 Paper 1 113 Paper 2 119 Paper 3 125 Answers 126 – 142 Contents ii
MUST KNOW Mnemonics Mnemonics (Chapter 6) 1 @ Pan Asia Publications Sdn. Bhd. Mnemonics (Chapter 6) 7 @ Pan Asia Publications Sdn. Bhd. Mnemonics (Chapter 6) 3 @ Pan Asia Publications Sdn. Bhd. Mnemonics (Chapter 6) 9 @ Pan Asia Publications Sdn. Bhd. Mnemonics (Chapter 6) 5 @ Pan Asia Publications Sdn. Bhd. Mnemonics (Chapter 8) 11 @ Pan Asia Publications Sdn. Bhd. BLUE RED sister loves SOUR plum BLUE litmus paper turns RED (Acid) Acid, Base and Salt Acid, Base and Salt Acid, Base and Salt Acid, Base and Salt Acid, Base and Salt Manufactured Substances in Industry • White precipitate in sodium hydroxide solution are ZAP MgCa (Pronounced as “ZAP MeCa”) • Soluble salt, NO SPA NO SPA Sodium Ammonium Potassium NO3 – • Insoluble salt PBC – Sulphate HPA – Chloride P ← PbSO4 B ← BaSO4 C ← CaSO4 H ← Hg2 Cl2 P ← PbCl2 A ← AgCl • White precipitate in ammonia solution are Zn MgPA (Pronounced as “Zinc Mengapa”) Add a little sodium hydroxide solution Add a little ammonia solution No precipitate No precipitate Heat up and test with red litmus paper NH4 + NH4 + , Ca2+ NH4 + Zn MgPA Zn2+ Al3+ Mg2+ Pb2+ Al3+ ZAP Zn2+ Al3+ Pb2+ Zn Zn2+ MgCa Mg2+ Ca2+ MgPA Mg2+ Pb2+ Al3+ White precipitate formed White precipitate formed Add excess ammonia solution and shake evenly Add excess sodium hydroxide solution Precipitate dissolves Precipitate does not dissolve • “Angcle Basuh Ferrari dgn Susu Pekat Nestle” (Pronouced as Bronchus) Bron Bronze Cu Copper Sn Tin (Pronouced as Zip cobra) Zip Zinc Cu Copper bra Brass (Pronouced as Steel IC) Steel Steel I Iron C Carbon Any acid CO3 2– HNO3 AgNO3 Cl– HNO3 Ba(NO)3 SO4 2– H2 SO4 Fe2 SO4 H2 SO4 pekat NO3 – Ang Ba Cle suh Nestle Susu pekat Ferrari ZAP MgCa Zn2+ Al3+ Pb2+ Mg2+ Ca2+ Precipitate dissolves Precipitate does not dissolve
Electron Symbol: e– Relative charge: –1 Relative mass: 1 1 840 Proton Symbol: p Relative charge: +1 Relative mass: 1 MUST KNOW Important Facts Important Facts (Chapter 2) 13 @ Pan Asia Publications Sdn. Bhd. Important Facts (Chapter 6) 19 @ Pan Asia Publications Sdn. Bhd. Important Facts (Chapter 3) 15 @ Pan Asia Publications Sdn. Bhd. Important Facts (Chapter 7) 21 @ Pan Asia Publications Sdn. Bhd. Important Facts (Chapter 5) 17 @ Pan Asia Publications Sdn. Bhd. Important Facts (Chapter 8) 23 @ Pan Asia Publications Sdn. Bhd. Valence electron Delocalised electrons from “sea of electrons” + + + + + + + + + + + + + + + + + + + + + + + + + Positively charged metal ion + + + + + + + + + + + + + + + + + + + + + + + + + Neutron Symbol: n Relative charge: 0 (neutral) Relative mass: 1 Mass Number of moles, n Volume of gas Number of particles: atom, molecules, ions ÷ Molar volume ÷ Molar mass ÷ NA ÷ NA × Molar volume × Molar mass Matter and the Atomic Structure Acid, Base and Salt The Mole Concept, Chemical Formula and Equation Chemical Bond Rate of Reaction Manufactured Substances in Industry • Only the sulphate salts below decompose when heated. FeSO4 → Fe2 O3 + SO2 + SO3 ZnSO4 → ZnO + SO3 CuSO4 → CuO + SO3 (NH4 )2 SO4 → 2NH3 + H2 SO4 Ammonia gas Sulphuric acid vapour • All chloride salts ARE NOT decomposed by heat, except ammonium chloride. NH4 Cl → NH3 + HCl Ammonia Hydrogen gas chloride gas • Most metal carbonates decompose to form metal oxides and carbon dioxide gas when heated. • However, potassium carbonate and sodium carbonate ARE NOT decomposed by heat. • Collision Theory. • Factors affecting the rate of reaction ❖ Size of reactant ❖ Concentration ❖ Temperature ❖ Catalyst • When frequency of collision between particles increases, frequency of effective collision between particles increases. This causes the rate of reaction to increase. • Diagram shows the relationship between number of moles, mass of substance, number of particles and volume of gas. • Metallic bond Type of alloy Composition Duralumin • Aluminium, 93%, • Magnesium, 3% • Copper, 3% • Manganese, 1% Bronze • Copper, 90% • Tin, 10% Brass • Copper, 70% • Zinc, 30% Steel • Iron, 99% • Carbon, 1% Stainless steel • Iron,73% • Chromium, 18% • Nickel, 8% • Carbon, 1% Pewter • Tin, 95% • Antimony, 3.5% • Copper, 1.5%
MUST KNOW Important Diagrams Important Diagrams (Chapter 2) 25 @ Pan Asia Publications Sdn. Bhd. Important Diagrams (Chapter 7) 31 @ Pan Asia Publications Sdn. Bhd. Important Diagrams (Chapter 2) 27 @ Pan Asia Publications Sdn. Bhd. Important Diagrams (Chapter 7) 33 @ Pan Asia Publications Sdn. Bhd. Important Diagrams (Chapter 6) 29 @ Pan Asia Publications Sdn. Bhd. Important Diagrams (Chapter 7) 35 @ Pan Asia Publications Sdn. Bhd. Matter and the Atomic Structure Rate of Reaction Matter and the Atomic Structure Acid, Base and Salt Rate of Reaction Rate of Reaction • Graph of temperature against time for the heating of naphthalene is shown below. • Graph of temperature against time for the cooling of naphthalene is shown below. Exothermic reaction Endothermic reaction Ea Ea ' Energy Reactants Products Without catalyst With catalyst Reaction pathway Ea Ea ' Energy Reactants Products Without catalyst With catalyst Reaction pathway Temperature (°C) 80°C A B C D Time (min) Temperature (°C) 80°C P Q R S Time (min) More acidic Neutral More alkaline 012 3 4 567 8 9 10 11 12 13 14 H H Collide Bond breaking and bond formation ● Correct orientation ● Total energy greater than or equal to the activation energy ● Effective collision occurs Cl Cl H H Cl Cl H H Cl Cl H Collide ● Wrong orientation ● Total energy greater than or equal to the activation energy ● Ineffective collision occurs Cl Cl H H Bounce off Cl Cl H H H Collide ● Correct orientation ● Total energy less than the activation energy ● Ineffective collision occurs Cl Cl H H Bounce off Cl Cl pH stands for 'hydrogen potenz' (hydrogen power) • Wrong orientation • Total energy greater than or equal to the activation energy • Ineffective collision occurs • Correct orientation • Total energy greater than or equal to the activation energy • Effective collision occurs • Correct orientation • Total energy less than the activation energy • Ineffective collision occurs
1 Chapter 1 Introduction To Chemistry NOTES 1.1 Development in Chemistry Field and Its Importance in Daily Life 1. The word 'chemistry' is believed to be originated from the Arabic word 'Al-kimiya'. 2. Chemistry is defined as one of the fields of science that studies the structures, properties, compositions and interactions between matters. 3. The table below shows various chemicals commonly used in agriculture, industry, food and medicine. Food Preservative Colouring Flavouring Agriculture Pesticide Herbicide Fertiliser Medicine Analgesic Antibiotic Antiseptic Industry Polymer Glass Ceramic Alloy 4. Researches in various chemistry fields have been carried out every day. 5. The need for chemical technology to solve problems spurs the development of chemical technology. 6. The following table shows careers that require knowledge in chemistry. Field Career Job scope Biotechnology Biochemist Study the chemical processes in living things Nanotechnology Nanotechnology engineer Learn new things that can change the health, science, technology, and the environment on a molecular level Nutrition Dietitian Expert in human nutrition who alters patients' diet based on their medical conditions and individual needs Nutritionist Study the nutritional value of food Cosmetology Cosmetic chemist Formulates skin care, personal care and colour cosmetics for manufacturers. Pharmaceutical Pharmacist Study medicine, drugs and their effects 1.2 Scientific Investigation in Chemistry 1. Scientific investigation is a systematic scientific method used to solve science related problems. 2. Steps involved in a scientific method: Making observation Making inference Making hypothesis Identifying problem Identifying variables Controlling variables Writing report Making conclusion Interpreting data Collecting data Planning experiment 1.3 Usage, Management and Handling Of Apparatus and Materials 1. The laboratory is an important place to study chemistry. However, this place can become dangerous if we do not obey the laboratory rules and practise the safety measures.
3 Each question has four different answers, A, B, C and D. For each question, choose one answer only. PAPER 1 1.1 Development in Chemistry Field and Its Importance in Daily Life 1. The word ‘Chemistry’ is believed to be originated from A Latin word C Arabic word B Malay word D English word 2. Which of the following statements is true about Chemistry? A Chemistry studies all matters in the Earth’s crust. B Chemistry is the study of the structure of living things. C Chemistry relates the matters that make up the universe. D Chemistry is the study of structures, properties, compositions, and interactions between matters. 3. Which of the following is not an example of chemicals? A Fibre C Energy B Balloon D Liquefied gas 4. Which substance is used to kill weeds? A Fungicide C Pesticide B Herbicide D Carbide 5. Which of the following chemicals is used to prevent the oxidation of food? A Stabiliser C Preservative B Thickener D Antioxidant 6. Sodium nitrite is added to burger so that the burger meat can last longer. What is the function of sodium nitrite? A Flavouring C Colouring B Preservative D Stabiliser 7. Which of the following requires the knowledge of chemistry? A Lawyer C Carpenter B Pharmacist D Plumber 8. The following statement refers to a type of occupation. He studies and determines the nutrient levels of food by analysing their contents. He also finds the best way to distribute, process, preserve and package food. Based on the statement above, what is his career? A Nanotechnology engineer C Nutritionist B Food scientist D Dietitian 1.2 Scientific Investigation in Chemistry 9. Which of the following is the first step in a scientific method? A Identifying problem C Making hypothesis B Making observation D Making inference 10. Which step in a scientific method is used to verify if the inference is true or false? A Planning an experiment B Controlling variables C Making observation D Making hypothesis 11. Mei Yu is giving an explanation about the event she has observed based on her past experience. Which step in a scientific method is she applying? A Making inference B Identifying problem C Making hypothesis D Identifying variables 12. Which of the following is the early logical conclusion? A Inference C Hypothesis B Conclusion D Data interpretation 13. How to test if the hypothesis made is correct? A Carrying out experiment C Collecting data B Planning an experiment D Interpreting data 14. What is a manipulated variable? A Factor that changes accordingly B Factor that remains the same in the experiment C Factor that can be measured with measuring instruments D Factor that is purposely changed to see the effect of other variables 15. To relate a manipulated variable and a responding variable in order to explain the question that has been asked is a step to A collect data B interpret data C make a conclusion D construct a hypothesis 3 3SOS TIP Question 3: Chemical is a matter. It must have mass and occupies space. Question 10: Based on observation, an inference (early conclusion) can be made to explain the observation. To verify the explanation of the observation, a hypothesis is constructed. Experiment is carried out to test if the hypothesis made is accepted or rejected.
19 52. Phosphorus-31 and phosphorus-32 are isotopes. Which statement is correct? HOTS Applying [Proton number of phosphorus = 15] A Phosphorus-31 has 15 protons and 16 electrons B Phosphorus-32 has 15 electrons and 17 neutrons C Phosphorus-31 has a smaller number of electrons than phosphorus-32 D Phosphorus-31 has the same number of neutrons as phosphorus-32 53. Diagram 22 shows the symbol used to label the food that is irradiated with isotope Q. Diagram 22 What is isotope Q? A carbon-14 C phosphorus-32 B sodium-24 D cobalt-60 CLONE SPM CLONE SPM 54. A food technologist intends to destroy bacteria by treating the food with radiation. Which of the following is suitable to be used? A Lead-210 C Carbon-14 B Cobalt-60 D Hydrogen-3 55. Diagram 23 shows a person suffering from a disease. Diagram 23 Which of the following is suitable to treat the disease? A Cobalt-60 B Iodine-131 C Sodium-24 D Magnesium-24 CLONE SPM CLONE SPM 19 19SOS TIP Question 55: Cobalt-60 is usually used to treat cancer but iodine-131 is specifically used to thyroid cancer. Question 1: (b) Types of particles refer to atom, molecule or ion. (c) Melting point = freezing point. Freezing point of pure water is 0ºC and boiling point of pure water is 100ºC. Section A Answer all questions. 1. Water has the formula of H2 O. Diagram 1 shows the arrangement of water particles in three states of matter X, Y and Z. X Y Z Diagram 1 (a) What are the physical states labelled X, Y, and Z? [3 marks] X : Y : Z : (b) What type of particle is found in water? [1 mark] (c) State the melting point of pure water. [1 mark] CLONE SPM PAPER 2
25 PAPER 3 You have to determine the melting point of a given substance T in a plastic pack. Using the apparatus supplied, carry out an experiment to determine the melting point of the substance T. The following are the brief steps of experiment: 1. Heat the substance T until the temperature reaches 70 °C. 2. Start the stopwatch instantly. 3. Record the temperature of substance T at 30-second intervals until the temperature reaches 90 °C. (a) Record the thermometer readings. [3 marks] (b) Plot a graph of temperature against time in a graph paper. [5 marks] (c) Based on the graph plotted, mark and label the melting point substance T. [3 marks] (d) Explain why the temperature of substance T remains the same for a period of time. [2 marks] (e) State the physical state(s) of substance T during [3 marks] (i) 0 s (ii) 90 s (iii) 210 s Note: If you are not able to carry out the experiment as described above, observe the thermometer readings and record the temperature in the space provided. Then, answer the question using the data you have recorded. Time (s) Thermometer reading Temperature (°C) Time (s) Thermometer reading Temperature (°C) 0 70 60 (i) 120 80 70 (v) 30 80 70 (ii) 150 80 70 (vi) 60 80 70 (iii) 180 90 80 (vii) 90 80 70 (iv) 210 90 80 (viii) 25SOS TIP Question 3: (a) When recording the thermometer reading, consider the accuracy of the thermometer by putting the correct decimal place. Do not put unit as the unit is on the heading of the table. (c) Make sure you draw the dotted line to indicate how you determine the melting point.
26 Chapter 3 The Mole Concept, Chemical Formula and Equation NOTES 3.1 Relative Atomic Mass and Relative Molecular Mass 1. The mass of an atom when compared to a standard atom is called relative atomic mass, RAM. Relative atomic mass has no unit because it is not the actual mass but only a comparison value. Standard atom Why is it chosen Carbon-12 The mass of one carbon-12 atom was assigned 12 units. • Carbon-12 was used as the reference standard in mass spectrometers. • Most elements combine with carbon-12. • Exists as a solid at room temperature and easy to handle. 2. Based on the carbon-12 scale, the relative atomic mass of an element is the average mass of one atom of the element when compared with 1 12 of the mass of one carbon-12 atom. Relative atomic mass (RAM) = Average mass of one atom of the element 1 12 × Mass of one carbon – 12 atom 3. Relative molecular mass of a molecule is defined as the average mass of the molecule when compared with 1 12 of the mass of one carbon-12 atom. Relative molecular mass (RMM) = Average mass of one molecule 1 12 × Mass of one carbon – 12 atom 4. The term ‘relative molecular mass’ can only be used for substances that are made up of molecules. For ionic compounds, the ‘relative formula mass (RFM) is used instead. 3.2 Mole Concept 1. One mole, with the symbol ‘mol’ of substance is defined as: Substance that contains 6.02214076 × 1023 elementary entities of the substance. 2. Avogadro constant, NA is defined as the number of particles in one mole of a substance. In other words, 1 mol of substance contains 6.02 × 1023 particles that form the substance. 3. When we say, 2 pairs of shoes, it means 2 × 2 = 4 shoes. If we were to say 2 dozen of shoes, that means 2 × 12 = 24 shoes. 4. What if we say 2 moles of shoes? It means 2 × 6.02 × 1023 = 1.204 × 1023 shoes. Number of moles, n Number of particles Atom // molecule // ion Number of moles, n = Number of particles NA × NA ÷ NA 5. The molar mass is the mass of one mole of the substance. 6. The molar mass of a substance contains 6.02 × 1023 particles of the substance. 7. The unit of molar mass is g mol–1. Number of moles, n Mass Number of moles, n = Mass Molar mass × molar mass ÷ molar mass 8. The molar volume of a gas is the volume occupied by one mole of the gas or 6.02 × 1023 particles of the gas. 9. The unit of molar volume is dm3 mol–1. 10. Under the same temperature and pressure, an equal number of moles of any gas will have the same volume. 11. The molar volume depends on the conditions. Molar volume Standard temperature and pressure, STP: Temperature = 0 °C Pressure = 1 atm Room conditions: Temperature = 25 °C Pressure =1 atm 22.4 dm3 mol–1 24 dm3 mol–1 22400 cm3 mol–1 24 000 cm3 mol–1
27 Number of moles, n Volume Number of moles, n = Volume Molar volume × molar volume ÷ molar volume 3.3 Chemical Formula 1. Chemical formula is a representation of a chemical substance using letters to represent the atoms and subscript numbers to show the numbers of each type of atoms found in the elementary entities of the substance. 2. From the chemical formula, we know: Water is made up of hydrogen and oxygen Relative molecular mass = 2(1) + 16 = 18 Ratio of hydrogen to oxygen = 2 : 1 2 hydrogen atoms 1 oxygen atom H2 O 3. Molecular formula can only be determined if we know the empirical formula and molar mass OR relative molecular mass of that substance. Molecular formula = (Empirical formula)n n × empirical formula = molar mass 4. Chemical formulae Empirical formula Formula that shows the simplest whole number ratio of atoms of each element in a compound Formula that shows the actual number of atoms of each element in the molecule of a compound Molecular formula 3.4 Chemical Equation 1. A chemical equation is a precise description of a chemical reaction. 2. Chemical equation gives us: (a) Qualitative information – Tell us the reactants and products involved in the reaction and the physical states of the reactants and products. (b) Quantitative information – Tells us the exact proportions (number of moles) of reactants and products in the reaction. Each question has four different answers, A, B, C and D. For each question, choose one answer only. PAPER 1 3.1 Relative Atomic Mass and Relative Molecular Mass 1. Why was carbon-12 chosen as the standard atom to determine the relative atomic mass of other elements? A Carbon has three isotopes. B Carbon is a solid and easier to be handled. C Carbon is heavier than oxygen and hydrogen. D Carbon is located in Group 14 in the Periodic Table of Elements. 2. A compound with formula X2 CO3 has a relative formula mass of 138. What is the relative atomic mass of X? HOTS Applying [Relative atomic mass: C=12, O=16] A 39 C 78 B 69 D 110 3. Ahmad filled four different types of gases into four balloons as shown in Diagram 1. 13 SPM CLONE SPM CLONE SPM W X Y Z CO2 C4H10 O2 N2 Diagram 1 Which balloon becomes the smallest after one day? HOTS Applying [Relative atomic mass: H = 1, C = 12, N = 14, O = 16] A W C Y B X D Z 4. The chemical formula for potassium hexacyanoferrate(II) is K4 Fe(CN)6 . What is its relative formula mass? HOTS Applying [Relative atomic mass: C = 12, N = 14, K = 39, Fe = 56] A 121 C 238 B 199 D 368 CLONE SPM 27 27SOS TIP Question 3: The smaller the size of particles, the easier the particles to penetrate through the semipermeable membrane. Therefore, the size of balloon will be reduced.
33 Section A Answer all questions. 1. (a) (i) What is the chemical formula of ammonia molecule? [1 mark] (ii) What is the name of the isotope of the element that is used as the standard to determine the relative atomic mass of other elements? [1 mark] (b) (i) What is the mass of 6.0 dm3 of ammonia gas, NH3 at room conditions? [2 marks] HOTS Applying [1 mol of gas occupies 24 dm3 at room conditions; molar mass of NH3 = 17 g mol–1] (ii) How many molecules are there in 6.0 dm3 of ammonia gas? HOTS Applying [1 mark] [Avogadro’s constant = 6.02 × 1023] (iii) Explain briefly the relationship between the volume, mass and the number of molecules of ammonia in 1(b) (i) and 1(b)(ii) at room conditions. [3 marks] 2. Atom is very small and it is impossible to weigh the mass of an atom using any electronic balance. Thus, chemist compares the mass of an atom with a standard atom. The mass obtained through comparison is called relative atomic mass. Diagram 1 shows the comparison of mass of lithium atom with 1 12 of carbon-12 atom. Li 1 12 of a carbon-12 atom 1 12 of a carbon-12 atom C-12 Diagram 1 (a) What is the meaning of relative atomic mass? [1 mark] CLONE SPM CLONE SPM PAPER 2 33 33SOS TIP Question 1: (b) (i) Number of moles Mass(g) Number of particles Volume of gas × NA ÷ NA × Molar volume × Molar mass ÷ Molar volume ÷ Molar mass (b) (iii) When explaining the relationship, relate the volume, mass and number of molecules to the number of moles.
38 Section B 7. (a) The following chemical equation shows the burning of carbon. 2C(s) + O2 (g) → 2CO(g) Based on the equation, give two qualitative information and one quantitative information. [3 marks] (b) A hydrocarbon X, consists of 82.75 % of carbon and 17.25 % of hydrogen by mass. The relative molecular mass of X is 58. (i) Determine the empirical formula of hydrocarbon X. [4 marks] (ii) What is the molecular formula of hydrocarbon X. [2 marks] (c) A good fertiliser will have a higher percentage of nitrogen by mass. Below are two types of fertilisers. Urea, CO(NH2 ) 2 (NH4 ) 3 PO4 Compare the percentage of nitrogen by mass for these fertilisers. Then, identify and explain which fertiliser is a better fertiliser. HOTS Applying [6 marks] [Relative atomic mass: H = 1, C = 12, N = 14, O = 16, P = 31] Section C 8. (a) The relative atomic mass of an atom of element is compared with the standard atom. HOTS Applying Using the idea above, find the (i) number of times 2 bromine atoms are heavier compared to 5 oxygen atoms. [Relative atomic mass: O = 16; Br = 80;] (ii) number of carbon atoms that have the same mass as 2 krypton atoms. [Relative atomic mass: C = 12; Kr = 84] [4 marks] (b) Diagram 5 shows two methods used in the laboratory to determine the empirical formula of a compound. Method I Method II Lid Crucible Magnesium ribbon Heat Dry hydrogen gas Chemical substance Heat Diagram 5 Compare these two methods with reference to the following aspects: HOTS Creating • Method used to determine the empirical formula of the metal oxide • Changes in the initial mass of the reactant and final mass of the product • Why there are changes in the mass of the reactant and the mass of the product? [6 marks] (c) Statement below is about metal Y. Metal Y is located higher than hydrogen in the reactivity series. Describe an experiment to determine the empirical formula of oxide of metal Y. HOTS Creating Your answer should include the procedure of experiment and calculation of the empirical formula. CLONE SPM 38SOS TIP Question 7: (c) Make sure you use the superlative adjective to explain the comparison. Question 8: (a) Consider the formula Number of atom P × RAM of atom P = number of times heavier × (number of atom Q × RAM of atom Q) (b) Refer to reactivity series to determine which method to be used to determine the empirical formula. (c) Only use unknown in the calculation. You are not required to create any data.
39 PAPER 3 You are required to determine the empirical formula of magnesium oxide. Referring to the Diagram 1, carry out the relevant experiment. The crucible and lid are weighed. The crucible, lid and magnesium ribbon are weighed. The magnesium ribbon is heated until it reacts completely with oxygen. The crucible, lid and magnesium oxide formed are weighed when cooled. ON OFF Lid Crucible Digital balance ON OFF Magnesium ribbon Magnesium Heat ON OFF White powder Diagram 1 (a) State two observations that can be obtained for the experiment. [2 marks] (b) State the corresponding inferences based on the observations in (a). [2 marks] (c) Record the reading to two decimal places for [3 marks] (i) Mass of crucible with lid: ...............g (ii) Mass of crucible with lid and magnesium ribbon: ...............g (iii) Mass of crucible with lid and magnesium oxide when cooled: ...............g (d) What is the mass of the magnesium and mass of oxygen used in the reaction? [3 marks] (e) Determine the empirical formula of magnesium oxide. [3 marks] [Relative atomic mass of Mg = 24; O = 16] (f) Referring to the answer in (e), determine the number of moles of magnesium that reacts with 2 moles of oxygen atoms. [3 marks] Note: If you are not able to carry out the experiment as described above, you can answer this question using the following samples of data: Mass of crucible with lid ON OFF Lid 38.4972 g Crucible Digital balance Mass of crucible with lid and magnesium ribbon ON OFF Magnesium ribbon 39.2210 g Mass of crucible with lid and magnesium oxide when cooled ON OFF White powder 39.7025 g 39SOS TIP Question (a): The observation does not include the change in the figure in electronic balance. Question (b): Inference is the early conclusion of the observation. It is actually the logical reason why an observation or phenomenon occurs.
54 Chapter 5 Chemical Bonds NOTES 5.1 Basics of Compound Formation 1. Most elements will combine with one another to form compounds. 2. Why should elements form compounds? Because compounds are more stable than free elements. The formation of compounds results in the formation of chemical bonds. 3. In the formation of chemical bonds, each atom will change its electron arrangement to achieve a stable electron arrangement through: (a) transfer of electrons (b) sharing of electrons 5.2 Ionic Bond 1. Ionic bond is a chemical bond formed through the transfer of electrons from a metal atom to a nonmetal atom. 2. The metal atom loses its valence electrons to achieve a stable duplet or octet electron arrangement. A cation is formed. 3. The electrons are transferred to the valence shell of the non-metal atom. 4. The non-metal atom gains electrons to achieve a stable octet electron arrangement. An anion is formed. 5. These oppositely charged ions are attracted to each other by strong electrostatic force. This strong electrostatic force results in the formation of ionic bond (electrovalent bond). 5.3 Covalent Bond 1. Covalent bond is a chemical bond formed from the sharing of valence electrons between non-metal atoms. 2. Non-metal atoms can be: (a) Elements of Group 15, 16, 17 (b) Carbon and silicon in Group 14 (c) Hydrogen 3. During sharing of electrons, the shared pair of electrons forms a covalent bond between two atoms. 4. The atoms that are bonded together by covalent bond produces a molecule. 5. There are 3 types of covalent bonds: Number of shared pair of electrons Example 1 X X Y or X Y Single covalent bond 2 X X X Y or X Y Double covalent bond 3 X X X X Y or X Y Triple covalent bond 5.4 Hydrogen Bond 1. There are some atoms with high electronegativity. These include oxygen, nitrogen or fluorine atoms. 2. Hydrogen bond is an attraction force between a hydrogen atom which is bonded to a high electronegativity atom, with either nitrogen atom, oxygen atom or fluorine atom in other molecules. 3. For example, the hydrogen bond that exists between two water molecules, H2 O. H O H H H O Covalent bond Hydrogen bond Oxygen atom, O with high electronegativity 4. Some of the phenomena that occur in daily life are closely related to hydrogen bonding, for example: (a) Wet hair that sticks to each other (b) Flipping pieces of paper more easily when fingertips are wet with water
55 5. The table below shows the melting point and boiling point of chlorine and ethanol. Substance Melting point ( o C) Boiling point ( o C) Chlorine –101.5 –34 Ethanol –114.1 78 6. Although the boiling points of both chlorine and ethanol are low, the boiling point of ethanol is much higher than that of chlorine due to the presence of hydrogen bonds between the two molecules. 7. More heat energy is required to overcome the van der Waals attraction forces between ethanol molecules besides breaking the hydrogen bonds between the ethanol molecules. 8. The solubility of ethanol in water is also due to the presence of hydrogen bond between ethanol molecule and water molecule. 5.5 Dative Bond 1. Dative bond is a covalent bond between two atoms in which the shared pair electrons are originated from one atom only. 2. Dative bond is also known as coordinate bond. 3. Hydroxonium ion and ammonium ion are two examples of ions with dative bond. (a) Hydroxonium ion + H + H+ H O H H H O Hydrogen ion without electron in the shell Hydroxonium ion that is formed through the formation of a dative bond. Lone paired electrons in a water molecule are contributed to the hydrogen ion to be shared together. (b) Ammonium ion + H + H H+ H N H H H N H Ammonium ion is produced through the formation of dative bond between hydrogen ion and nitrogen atom in the ammonia. 5.6 Metallic Bond 1. Metal atoms have 1, 2, or 3 valence electrons. 2. Even in solid state, valence electrons of metal atoms are easily released and delocalised. Positivelycharged metal ions are formed. 3. The delocalised valence electrons move freely between the metallic structure and form the sea of electrons. 4. Therefore, electrostatic force of attraction between the sea of electrons and metal ions is produced. Thus, a metallic bond is produced. Valence electron Delocalised electrons from “sea of electrons” + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Positively charged metal ion 5. Metals can conduct electricity because the delocalised valence electrons in the sea of electrons can move freely and carry electrical charges from the negative terminal to the positive terminal. 5.7 Ionic and Covalent Compounds 1. Electrical conductivity (a) In solid state, ionic compounds do not conduct electricity because the ions are attracted to each other by strong electrostatic forces. Hence, these ions cannot move freely. (b) Ionic compounds can conduct electricity in molten or aqueous states because ions can move freely and carry electrical charges. (c) Covalent compounds do not conduct electricity in all states because they are composed of neutral molecules. Free moving ions do not exist. 2. Solubility in Water and Organic Solvent (a) Most ionic compounds are soluble in water. (b) Ionic compounds do not dissolve in organic solvents. (c) Most covalent compounds are soluble in organic solvents. (d) Covalent compounds do not dissolve in water. 3. Melting and Boiling Points (a) Cations and anions in the lattice of ionic compounds are attracted to each other by strong electrostatic forces. More heat energy is required to overcome the strong electrostatic forces. (b) Due to high melting and boiling points, ionic compounds usually exist as non-volatile solids. (c) Molecules in covalent compounds are attracted to each other by weak van der Waals force of attraction. Less heat energy is needed to overcome the weak van der Waals forces of attraction between molecules. (d) Due to low melting and boiling points, covalent compounds usually exist as volatile liquids.
56 Each question has four different answers, A, B, C and D. For each question, choose one answer only. PAPER 1 5.1 Basics of Compound Formation 1. Ionic bond is formed when A non-metal atoms share electrons. B nucleus of atom attracts valence electrons. C nucleus of non-metal atoms attracts each other. D metal atoms transfer electrons to non-metal atoms. 2. Which atom forms a cation? A Chlorine C Sodium B Oxygen D Carbon 3. What is the meaning of covalent bond? A A bond is formed when metal atoms share electrons with each other to achieve a stable electron arrangement. B A bond is formed when non-metal atoms share electrons to achieve a stable electron arrangement. C A bond is formed when non-metal atoms transfer electrons to metal atoms. D A bond is formed when metal atoms transfer electrons to non-metal atoms. 4. Which statement best explains the formation of a covalent bond? A Metal atoms share electrons with non-metal atoms. B Non-metal atoms share electrons with non-metal atoms. C Metal atoms donate electrons while non-metal atoms accept electrons. D Non-metal atoms donate electrons while metal atoms accept electrons. 5. Diagram 1 shows the electron arrangement of a potassium ion. + K Diagram 1 What is the number of valence electrons of the potassium atom? A 1 B 7 C 8 D 9 CLONE SPM CLONE SPM CLONE SPM CLONE SPM 6. An atom of element E has 12 neutrons. The nucleon number of element E is 23. Atom E loses electrons to form ion E. How many electrons are there in ion E? A 1 C 10 B 8 D 11 5.2 Ionic Bond 7. Diagram 2 shows a snail. The snail shell contains a natural ionic compound. Diagram 2 Other than carbon, what elements are contained in the ionic compound? A Calcium and oxygen B Sodium and oxygen C Calcium and hydrogen D Sodium and hydrogen 8. Which substance is an ionic compound? A Carbon monoxide, CO B Sulphur trioxide, SO3 C Silicon dioxide, SiO2 D Magnesium oxide, MgO 9. Which compound is formed by transferring electrons? A Hydrogen chloride, HCl C Ammonia, NH3 B Lithium oxide, Li2 O D Oxygen, O2 10. Diagram 3 shows the electron arrangement of a chemical compound. Q Q + + R 2– Diagram 3 What are the elements represented by Q and R? Q R A Sodium Oxygen B Oxygen Sodium C Lithium Fluorine D Fluorine Lithium CLONE SPM CLONE SPM CLONE SPM CLONE SPM CLONE SPM 56SOS TIP Question 2: Cation is positive ion that is produced when a neutral atom loses its valence electron. Question 6: Nucleon number – proton number (number of protons) = number of neutrons Question 8: Ionic compound is formed when metal reacts with non-metal.
65 (c) Diagram 4.2 shows a lady is removing her nail polish using acetone. Acetone Diagram 4.2 Based on the diagram, answer the following. (i) Explain why acetone is suitable to be used to remove the nail polish. [2 marks] (ii) Can water replace acetone to remove the nail polish? Give your reason. [2 marks] 5. Table 1 shows the electrical conductivity and melting point of substances P, Q and R. Table 1 Substance Electrical conductivity in the state of Melting point (°C) Solid Molten Aqueous P No No No < -110 Q No No No 80 – 90 R No Yes Yes > 800 (a) (i) State the type of structure and bonding of substance P. [2 marks] Structure: Bonding: (ii) Explain why substance P has a low melting point but substance R has high melting point. HOTS Analysing [4 marks] (b) State how the bonds are formed in: (i) substance Q. [1 mark] (ii) substance R. [1 mark] (c) State why substance R can conduct electricity in molten and aqueous states but not in solid state. [2 marks] CLONE SPM 65SOS TIP Question 4: (c) (ii) You need to figure out the type of compound of nail polish. Consider if the compound is able to dissolve in the organic solvent. Question 5: (a) (i) There are two structures in covalent compound, namely, simple molecular structure and giant molecular structure.
68 PAPER 3 You are required to compare the electrical conductivity of molten X and molten Y. Prepare the apparatus set-up as in Diagram 1 and carry out the experiment according to the given procedure. Procedure: 1. Fill a crucible with solid X until it is half full. 2. Place carbon electrodes into the solid X. 3. Complete the circuit by connecting carbon electrodes to switch, bulb and batteries. 4. Turn on the switch and observe whether the bulb is lighted up. Turn off the switch. 5. Then, heat the solid X until it is melted. Turn on the switch again and observe whether the bulb is lighted up. 6. Steps 1 to 5 are repeated using solid Y. Based on the experiments carried out, answer the following. (a) Complete the Table 1. [6 marks] Table 1 Compound Physical state Observation Inference X Solid Molten Y Solid Molten (b) For this experiment, state the [3 marks] (i) manipulated variable (ii) responding variable (iii) constant variable (c) State one hypothesis for this experiment. [2 marks] (d) State the operational definition of electrical conductivity this experiment. [2 marks] (e) Explain why molten sulphur cannot conduct electricity. [2 marks] Note: If you are not able to carry out the experiment as described above, you can answer this question using the following samples of data: Compound Physical state Observation Inference X Solid Bulb does not light up Compound X conducts electricity in molten Molten Bulb is lighted up state but not in solid state. Y Solid Bulb does not light up Compound Y cannot conduct electricity in solid Molten and molten states. Bulb does not light up Batteries Bulb Switch Crucible Heat Carbon electrodes Solid X Diagram 1
126 CHAPTER 1 Paper 1 1. C 2. D 3. C Energy is not a matter. Therefore, it is not a chemical as well. 4. B Fungicide is to kill fungi, pesticide is to kill pest. 5. D Stabiliser is used to mix oil or fat and water together without separating. Thickener is to thicken the food and preservative is used to slow down the rate of food decaying process. 6. B Sodium nitrite is a preservative to make the meat lasts longer. 7. B 8. B Nutritionist studies the nutritional value of the food. Dietitian is an expert in human nutrition and alters the patient's diet based on their medical condition and individual needs. Nanotechnology engineer learns new things that can change the health, science, technology, and the environment on a molecular level. 9. B 10. D Hypothesis is to verify the inference whether it is true or not. 11. A Making inference means making explanation of an observation based on past experience. 12. A 13. A In order to test the hypothesis, an experiment is conducted. 14. D 15. D Hypothesis is a statement that relates the manipulated variable with the responding variable. 16. B 17. C 18. B 19. C 20. B 21. B 22. A 23. B The mass of beakers and volume of beakers do not affect the result of the experiment. The type of salt used (soluble or insoluble), will affect the result of experiment and must be kept constant. 24. C 25. B Eyewash is a safety equipment in the laboratory. 26. A Safety goggles is actually a personal protective equipment a person should wear when handling dangerous experiment. 27. A 28. C Eyewash is a safety equipment to clean the parts of the eye in case of accident. 29. D Fume chamber is a cupboard that is used to carry out experiment that involves the release of toxic gas. Answers Chapter 1 30. A 31. A Fractional distillation is to separate petroleum fractions based on their differences in the boiling points. 32. B Ethanol boils around 78˚C, whereas water boils at 100˚C. Therefore, distillation is used to separate the ethanol that is dissolved in the water. 33. B Burette can measure accurately the volume of solution up to two decimal places in its accuracy. 34. B 35. C Phenolphthalein changes from pink to colourless when the alkaline solution is neutralised upon reaching end point. 36. B Gas coming out from the anode is oxygen gas. So, it is tested using a glowing splinter. 37. A 38. A 39. A Alkali metal is very reactive and tends to react with water and oxygen in the air. 40. A Hydrocarbon is flammable and should be kept away from heat source. 41. A Silver nitrate can be easily decomposed. Therefore, it must be kept away from sunlight. 42. B Mercury, lead, arsenic, cadmium and chromium are examples of heavy metals. 43. C Poisonous chemicals must be stored properly and cannot be reached easily. So it has to be locked in cabinet. 44. D 45. C Adding water to concentrated acid may be very exothermic and the heat released may vapourise the corrosive acid. Always add acid to the water (remember 3A: Always Add Acid to the water) 46. D 47. B 48. D 49. D 50. A Writing a report is to keep a documentation for reference in the future. Data collected cannot be altered and scientist should be honest in recording the results obtained. More measurements should be done to get average value of measurement to increase the accuracy. Paper 2 Section A 1. (a) A field of science that studies the structures, properties, compositions and interactions between matters. (b) (i) Insecticide, colouring and detergent (ii) Insecticide: to kill insect Colouring: to give colour or restore colour loss during food processing Detergent: to clean fabrics (c) (i) Cosmetic consultant (ii) Biotechnologist (iii) Nutritionist 2. (a) A systematic scientific method used to solve science related problems. (b) (i) Manipulated variable: Total surface area exposed to sunlight Responding variable: Rate of evaporation (ii) Unfolded filter paper dries first but folded filter paper still wet. (iii) The bigger the exposed surface area, the higher the rate of evaporation. (c) Making observation, making inference, identifying problem, making hypothesis, identifying variables, controlling variables, planning experiment, collecting data, interpreting data and making conclusion. 3. (a) Do not eat, drink, chase or run in the laboratory. Do not pour the chemicals back to the reagent bottles. (b) Use safety goggles when mixing or heating chemicals. Keep flammable substances away from the heat source. (c) (i) To avoid dust or splashes of chemicals accidentally get into the eyes (ii) To protect respiratory organs from toxic chemicals, either in the form of powder or fumes (iii) To protect hands from any injury, exposure to chemicals or infection 4. (a) Potassium: Kept in paraffin oil Hydrogen peroxide: Kept in dark bottles Ethanol: Kept in shady area and far from sunlight and heat source (b) (i) Phenomenon at which a person is exposed to mercury in a certain amount either accidentally inhaled the mercury vapour or touch the mercury spill until the mercury is absorbed into the body through the skin (ii) Nausea and vomiting (iii) Inform the accident to the teacher immediately. Next, make the spill site a restricted area. Sprinkle sulphur powder to cover up the mercury spill. Lastly, contact the Fire and Rescue Department for further action. Section B 1. (a) Put some alkaline quicklime or slaked lime to neutralise the acidity of the soil.
139 26. B Sulphuric acid is a strong diprotic acid. It has the highest concentration of H+ ions. 27. D 28. D Zinc powder in Experiment II has bigger total surface area. Rate of reaction of Experiment II is higher. The volume of gas produced is the same since the volume and concentration of acid used are the same. 29. C Curve Q represents higher rate of reaction. Therefore, higher concentration of hydrogen peroxide is needed. The volume of gas produced in curve Q is lesser. So, the number of moles of hydrogen peroxide should be lesser. 30. A Higher concentration of acid produces higher rate of reaction with steeper gradient. Number of moles of hydrochloric acid is higher. So, the volume of gas produced will be greater. 31. C 350 kg 300 min = 1.167 kg min–1 200 kg 120 min = 1.67 kg min–1 120 kg 60 min = 2 kg min–1 100 kg 90 min = 1.11 kg min–1 In one minute, 2 kg of sulphur trioxide is produced under 450ºC. 32. D 33. D Higher temperature increases the kinetic energy of reacting particles. 34. D Heating the acid will increase the temperature of hydrochloric acid. At higher temperature, rate of reaction is higher. Copper (II) sulphate should be the catalyst of the reaction. When more water is added, the concentration of acid decreases and this will reduce the rate of reaction. 35. A Catalyst provides an alternative path with lower activation energy. 36. C 37. A Sulphuric acid is a strong diprotic acid. It has the highest concentration of H+ ions. 38. A Catalyst provides an alternative path with lower activation energy. 39. A 40. D 41. D Manganese (IV) oxide acts as a catalyst in decomposition of hydrogen peroxide. 42. D Changing the concentration or volume will affect the number of moles of hydrogen peroxide and results in different volume of gas released. 43. A Reduce the size will increase the total surface area of zinc that reacts with acid. 44. B Fine salt dissolves faster. There is 0.02 g of salt per 1 cm3 of water in A but there is only 0.015 g of salt per 1 cm3 of water in B. Therefore 3 g of salt dissolves faster in 200 cm3 of water. 45. B Higher temperature and concentration of the solution will increase the rate of reaction. 46. D 47. A Higher pressure also results in higher temperature according to pressure’s law. 48. D In the reaction, copper (II) sulphate solution acts as catalyst. Magnesium powder has larger total surface area compare to magnesium ribbon. 49. C Effective collision is the collision which causes a chemical reaction. 50. B Increase in temperature will increase the kinetic energy of the reacting particles. Thus, increasing the frequency of collision between reacting particle. 51. A 52. C Number of moles of reactants should be the same because produces equal amount of hydrogen gas. Paper 2 1. (a) (i) Change in the volume of hydrogen gas per unit time. (ii) 2HCl + Zn → ZnCl2 + H2 (iii) Change in the volume of gas. (iv) Size of zinc (b) When potatoes are cut into smaller pieces. At smaller size, total surface area exposed to hot water is bigger. More heat is absorbed to cook the potatoes. (c) Rusting and photosynthesis 2. (a) Zn + H2 SO4 → ZnSO4 + H2 (b) (i) All sulphuric acid is used up. (ii) 1.75 g (c) Zinc Water Hydrogen gas Burette Basin Sulphuric acid (d) (i) At higher temperature, kinetic energy of particles increases and particles move faster. Particles also gain extra energy to overcome the activation energy. Frequency of collision between H+ ions and zinc atoms increase. Frequency of effective collision between H+ ions and zinc atoms also increase. (ii) t1 Time (s) Mass of zinc (g) The curve at the temperature of 30 °C 5.00 1.75 3. (a) (i) Set I: Average rate = 30 1.5 = 20 cm3 min–1 Set II: Average rate = 50 1.5 = 33.33 cm3 min–1 (ii) Rate of reaction in Set II is higher (iii) At higher temperature, kinetic energy of particles increases and particles move faster. Particles also gain extra energy to overcome the activation energy. Frequency of collision between H+ ions and calcium carbonate in Set II is higher. Frequency of effective collision between H+ ions and calcium carbonate in Set II is higher. (b) (i) &(ii) Ea Ea ' Reaction path Energy Zn + 2HNO3 Zn(NO3 ) + H2 4. (a) Size of calcium carbonate. (b) Measure the change in the volume of carbon dioxide per unit time. (c) Change in the volume of carbon dioxide gas can be observed and measured using burette. (d) Temperature and concentration hydrochloric acid. (e) (i) Experiment II. Gradient of the curve in experiment II is higher. (ii) All hydrochloric acid and calcium carbonate are fully used up. (iii) Volume of gas collected is the same. Number of moles of carbon dioxide gas in both experiments are the same Number of moles of acid and calcium carbonate used in both experiments are also the same. Chapter 7